The present invention relates to a method for producing a surface mounting optoelectronic component comprising a base body, an optoelectronic transmitter and/or receiver that is arranged in a recess of the base body, and an optical device that occludes the recess, as well as to a surface mounting optoelectronic component.
In recent years, surface mounting technology (SMT) has increasingly supplanted the equipping of conductor carriers with wired components. The crucial advantage of SMT is an increase in packing density, which cannot be achieved by conventional insertion methods.
Due to the high packing density, which is desirable in many optical applications, SMT is particularly important in the field of optoelectronics. There are already known optoelectronic components which are designed to be surface mounted in accordance with the SMT concept.
European patent application No 230 336 therefor describes a surface mounting optoelectronic component that comprises an annular housing, the upper opening of which is sealed by a ball lens, while the lower opening of the ring stands on a printed circuit board. Inside the housing, a light-emitting semiconductor element is arranged between the present circuit board and the bottom vertex of the ball lens. The interior space of the ring housing, which is defined by the surface of the printed board and the ball lens, is filled with a transparent glue.
Another surface mounting optoelectronic component is illustrated in EP 0 400 176. This component has a base body with a central depression in which an optically active semiconductor element is arranged. Above the base body, there is a lens, which is connected to the base body via a fixing mechanism such as a clamping peg.
xe2x80x9cSiemens SMT-TOPLED fxc3xcr die Oberflxc3xa4chenmontagexe2x80x9d (Frank Mxc3x6llmer and Gxc3xcnter Waitl, Siemens Components 29 (1991), Vol. 4:147-149) teaches a light emitting diode (LED) which is provided for surface mounting. To produce this diode, a continuously stamped conductor strip is coated with a thermally stable thermoplast, forming the housing frame. In the inner region of the housing frame, an optically active element is mounted on the conductor strip and electrically contacted to interconnects there. Next, the frame""s interior region for guarding the active element against environmental influences is cast using a casting resin. A lens or similar optical device is not provided in this component.
The SMT opto-components described in the documents cited above have the unique attribute that first the whole component housing is produced by coating a conductor strip with a thermoplast material, and the opto-electronic transmitter and/or receiver is inserted into the thermoplast housing only after this is produced. The advantages of this method of production are that a very economical mass production at the belt (conductor strip) is possible, and low structural heights and standardized basic structural forms are easy to realize. Due to their low costs, these prehoused SMT opto-components, as they are called, are used above all in display arrays and the like.
It is the object of the present invention to set forth a method by which the emission characteristic of opto-electronic SMT components of the above type can be improved without raising the component costs unacceptably. The present invention is also directed to designing this type of optoelectronic SMT component with a well definable emission characteristic and simultaneously low component costs.
This object is achieved in accordance with the present invention in a method for producing a surface mounting optoelectronic component having a base body, an optoelectronic transmitter/receiver that is arranged in a recess of the base body, and an optical device that covers the recess, said method comprising the steps of: preparing the base body with the optoelectronic transmitter/receiver arranged in the recess; filling the recess of the prepared base body with a transparent hardenable casting compound; then placing the optical device onto the as yet uncured casting compound; and then curing the casting compound.
In an embodiment, the step of preparing the base body comprises the steps of: coating a conductor strip with a thermoplast housing while simultaneously forming the recess of the base body into a top surface of the thermoplast housing, a portion of said conductor strip being situated inside the recess; mounting the optoelectronic transmitter/receiver on said portion of the conductor strip situated inside the recess; and filling the recess of the base body with a transparent curable casting compound having thermal characteristics adapted to the thermoplast housing material.
In an embodiment, the recess of the base body is filled with the casting compound to a level such that, during the subsequent placement of the optical device, essentially no casting compound runs over an edge of the recess.
In an embodiment, the recess is filled with casting compound essentially to the edge of the recess such that, after the recess is filled with casting compound, a fillet develops owing to the surface tension of the casting compound; and the optical device has a shape in a region contacting the casting compound that no casting compound runs over the edge of the recess when the optical device is subsequently placed onto the casting compound.
In an embodiment, the optical device is placed from above, without pressure, onto one of the base body or at least one seating element attached to said base body within said recess.
In an embodiment, the casting compound is cured by the influence of heat.
In an embodiment, prior to filling the recess, an optical device is produced by one of casting, pressing, or injection processing; then the optical device is readied and transported as bulk material of optical devices; then a respective optical device is automatically picked from the bulk material; and then the picked optical device is automatically positioned over the base body.
This object is also achieved in accordance with the present invention in a method for producing a surface mounting optoelectronic component having a base body, an optoelectronic transmitter/receiver that is arranged in a recess of the base body, and an optical device that covers the recess, said method comprising the steps of: preparing the base body with the optoelectronic transmitter/receiver arranged in the recess; then filling the recess of the prepared base body with a first transparent hardenable casting compound; then readying a casting mold half and filling the mold half with a second transparent hardenable casting compound; then at least partially curing at least one of the first casting compound in the recess of the base body and the second casting compound in the mold half; then casting the optical device onto the base body by joining the base body and the mold half properly positioned, such that second casting compound in the mold half comes into contact with a surface of the first casting compound in the recess of the base body; then curing at least one of the second and first casting compound; and then removing the mold half from the base body with the cast-on optical device.
In an embodiment, the method further comprises, prior to joining the base body and the mold half, wetting the surface of the first casting compound.
In an embodiment, the step of wetting the surface of the first casting compound comprises the steps of: turning the base body about a horizontal axis such that an opening of the recess is directed downwardly; and at least superficially immersing the base body in liquid casting compound.
In an embodiment, the at least partial curing of the first casting compound is by heat treatment.
In an embodiment, the at least partial curing of the second casting compound is by heat treatment.
In an embodiment, the method further comprises the steps of: leading a number of base bodies on a first strip; and leading a number of mold halves on a second strip, wherein the first strip and the second strip are led in parallel at least during the step of casting the optical device onto the base body.
In an embodiment, the method further comprises the steps of: leading a number of base bodies on a first strip; combining a number of mold halves in a group; and connecting the group of mold halves, such that they can be detached, to a corresponding number of base bodies at least during the step of casting the optical device onto the base body.
In an embodiment, the base body and the mold half are joined at a temperature of approximately 80xc2x0 C.
In an embodiment, the second casting compound is cured at a temperature of approximately 150xc2x0 C.
In an embodiment, the mold half is removed from the base body at a temperature of approximately 80xc2x0 C.
This object is also achieved in accordance with the present invention in a surface mounting optoelectronic component comprising:
a base body having a thermoplast injection housing and a coated conductor strip secured to the housing, said base body having a recess formed therein with a portion of the conductor strip situated inside the recess;
an optoelectronic transmitter/receiver arranged in the a recess of the base body and mounted on the portion of the conductor strip situated inside the recess;
a transparent hardenable casting compound provided in the recess, said casting compound having thermal characteristics adapted to those of the thermoplast housing material; and
an optical device covering the recess and cast onto the casting compound such that a seating surface of the optical device is in surface-wide contact with the casting compound.
In an embodiment, the recess comprises a ring channel surrounding the recess.
In an embodiment, the base body comprises a number of seating elements for seating of the optical device, said seating elements being arranged at a margin side relative to the recess.
Following the production of the base body with the optoelectronic transmitter and/or receiver arranged in the recess, the recess of the base body is filled with a transparent hardenable casting compound, and the optical device is attached to the base body, said optical device being brought into contact with the casting compound in the region of the recess before the casting compound and/or the optical device (if this also comprises a casting compound) has completely hardened.
An essential aspect of the present invention is that the optical device is placed on the base body only after the recess is poured with casting compound. Because the optical device is placed onto the recess when the latter is already filled with casting compound, the optical device can be positioned on the base body extremely precisely and reproducibly, and this positioning remains essentially unaffected by subsequent steps such as curing or removal from the mold. This guarantees a high optical quality of the optoelectronic component with respect to the emission behavior or reception behavior, which is very important for applications in which an exact beam guidance and a high light yield are desirable. The present inventive optoelectronic components are thus superior to components in which the recess is filled from the reverse side given a previously mounted optical device.
The present inventive method can be applied particularly advantageously in the production of what are known as prehoused optoelectronic components. Here, the base body is produced first by coating a conductor strip with a thermoplast while the housing with the recess is simultaneously formed, and then the optoelectronic transmitter and/or receiver is assembled on a section of the conductor strip that resides in the recess.
In accordance with a first, particularly advantageous embodiment of the present inventive method, the optical device is placed on the as yet unhardened casting compound, and the casting compound is then cured.
In this case, the fill level of the casting compound can be selected such that casting compound does not escape over the edge of the recess when the optical device is placed on. It is then unnecessary to take measures to trap casting compound that may overflow.
It is also possible to exploit a fillet formation of the casting compound, which arises on the basis of its surface tension. In this case, an optical device is used whose shape in its region that contacts the casting compound is selected such that, even when the recess is filled to the edge with casting compound, said casting compound does not overflow the edge of the recess when the optical device is placed on.
The base body can also be provided with a ring channel that surrounds the recess before the optical device is placed on. In this case, casting compound that may overflow when the optical device is placed on is collected in the ring channel, thus preventing it from running down on the exterior of the base body and hardening there, which would impair the manipulability of the component.
A particularly reproducible positioning of the optical device is achieved when, prior to the placement of the optical device, the base body is provided with seating elements that are arranged at the margin side relative to the recess. The seating elements can be formed integrated with the housing in the above described injection step for producing the base body for a prehoused optoelectronic component.
Preferably, the optical device is placed from above onto the base body, or the seating elements that have been fashioned thereon, without pressure. The placement of the optical device then occurs by means of gravity alone.
In an embodiment, the optical device is first produced by means of a casting, pressing or injection procedure before the optical device is placed on, and then it is transported in bulk and placed onto a base body by automatic picking from the bulk material and automatic positioning over said base body. The advantage of these measures is that the optical device is produced completely independently of the production of the base body, opening up the possibility to control the quality of the optical device effectively and distinctly and to eliminate spoilage. This makes it possible to produce components of the highest quality.
In a second particularly preferred embodiment of the inventive method, the optical device is formed in a casting process, and in the scope of this casting process it is placed onto the base body in the region of the recess and is cast out with the casting compound in the recess. Also, in this second embodiment of the inventive method, the recess of the base body is filled before the optical device is placed on in the scope of said pouring process, so that the advantages associated with this procedure are also manifest in this embodiment of the invention.
In this second embodiment of the inventive present method for producing the optical device, one half of a casting mold is advantageously prepared first, and this half is filled with an additional casting compound. On the other hand, when the recess of the base body has been filled with casting compound, the casting compound is first hardened at least partially and is then wetted with casting compound. Next, the base body and the half of the casting mold which is filled with the additional casting compound are joined, under correct positioning, and in a following step the additional casting compound in the casting mold half is cured, whereby it is cast onto the casting compound in the recess of the base body. Last, the now finished optoelectronic component is ejected by removing the half of the casting mold from the base body with the optical device that has been cast on.
Wetting can be accomplished by turning the base body about a horizontal axis and immersing it in casting compound at least on the surface, for example. Because of the at least partial hardening of the casting compound, none of the compound escapes during the turning process.
The wetting of the surface of the casting compound prevents air bubbles from remaining in the casing compound in the subsequent casting on process.
The advantage of the described second embodiment of the inventive method is that it is particularly easy to realize and has a high potential for automatization, enabling mass productions [sic] on an industrial scale.